Soil Survey

1. Soil Survey Helping People Understand Soils Soil Taxonomy NRCS National Soil Survey Center Soil Survey Standards

2. Why is this topic important? Soil Survey Helping People Understand Soils • Soil Taxonomy (ST) is the basic language of soil classification for your profession. • You should become proficient in the parts of Soil Taxonomy that apply to the soils in your work area.

3. Objectives Soil Survey Helping People Understand Soils • You will be able to: • List 3 reasons we use Soil Taxonomy • List the 8 attributes of Soil Taxonomy • Describe the general concept for the categorical levels • Use the 2nd edition of ST and the Keys to Soil Taxonomy (KST) properly to classify soils

4. Purpose of Soil Taxonomy Soil Survey Helping People Understand Soils Provides a way to group soils that have similar properties and genesis • Groupings made at various map scales • Soil maps of large areas use small map scales (e.g., 1: 7.5 million) and the higher category taxa of order through subgroup • Soil maps of small areas use large map scales (e.g., 1:12,000) and lower category taxa such as family and series

5. Soil Survey Helping People Understand Soils

6. Purpose of Soil Taxonomy Soil Survey Helping People Understand Soils Facilitates communication among soil scientists • Ustert • Aquiturbel • Loamy, mixed, superactive, frigid Lithic Argixeroll Names of taxa are based on formative elements • The names of soil orders begin with a formative element and end in the Latin root sol (e.g., Aridisols) • Underlying taxa also contain the formative element (e.g., Vertic Natrigypsids)

7. Purpose of Soil Taxonomy Soil Survey Helping People Understand Soils Transfer of Information and Technology • “A Basic System of Soil Classification for Making and Interpreting Soil Surveys” (USDA, AH-436) • Estimated soil property data from sampling a few locations • Estimated productivity (crop yields, tree growth, etc.) • Estimated soil performance (suitability for houses, need for irrigation, need for lime and fertilizer, etc.)

8. 8 Fundamental Attributes of Soil Taxonomy(2nd ed. Chapter 2) Soil Survey Helping People Understand Soils 1.) Definitions are operational

9. 8 Fundamental Attributes of Soil Taxonomy Soil Survey Helping People Understand Soils 2.) Multicategoric System

10. 8 Fundamental Attributes of Soil Taxonomy Soil Survey Helping People Understand Soils 3.) Taxa represent real bodies of soil

11. 8 Fundamental Attributes of Soil Taxonomy Soil Survey Helping People Understand Soils 4.) Differentia are observable/inferable properties

12. 8 Fundamental Attributes of Soil Taxonomy Soil Survey Helping People Understand Soils 5.) Soil Taxonomy is (relatively) easy to modify as new knowledge & experience is gained

13. 8 Fundamental Attributes of Soil Taxonomy Soil Survey Helping People Understand Soils 6.) Native & cultivated pedons classified the same

14. 8 Fundamental Attributes of Soil Taxonomy Soil Survey Helping People Understand Soils 7.) All soils in the landscape can be accommodated

15. 8 Fundamental Attributes of Soil Taxonomy Soil Survey Helping People Understand Soils 8.) All soils known in the world are included

16. Concepts by Category (Level) Soil Survey Helping People Understand Soils Orders (12) Differentiated by properties resulting from major soil-forming processes

17. Concepts by Category (Level) Soil Survey Helping People Understand Soils Suborders (70) Differentiated by important properties, such as soil climate, exerting major controls on the current set of soil-forming processes

18. Concepts by Category (Level) Soil Survey Helping People Understand Soils Great Groups (344) Presence of key horizons, or other properties exerting subordinate controls

19. Concepts by Category (Level) Soil Survey Helping People Understand Soils Subgroups (2,664) Represent: 1) Overlapping of processes recognized in other taxa (intergrades) 2) Processes or conditions not recognized in other taxa (extragrades) 3) Others (Typic)

20. Concepts by Category (Level) Soil Survey Helping People Understand Soils Families (~11,332) -Groups soils in a subgroup that have similar physical and chemical properties that affect their response to management and manipulation for use

21. Concepts by Category (Level) Soil Survey Helping People Understand Soils Series (~23,600) -Properties are many of the same ones used as differentia at higher levels, whether used as the formative elements in the names of taxa - Used to differentiate natural bodies of soils within a family - Phases of series are not a category of ST

22. Using the Keys Correctly Soil Survey Helping People Understand Soils Know what to Classify (Ch. 1, KST) • Soil is defined as having either (genetic) horizons distinguished from parent material by Simonson’s 4 basic processes or • The ability to support rooted plants in a natural environment • Nonsoilbodies correlated as miscellaneous areas (deep water, barren lands, rock, or ice)

23. Using the Keys Correctly Soil Survey Helping People Understand Soils Know what to Classify (Ch. 1, KST) • Top (boundary between soil and air, shallow water, live plants, or undecomposed plant material) • Bottom (200 cm, lithic contact, 25 cm below paralithic or densic contacts) • There are rules for buried soils

24. Using the Keys Correctly Soil Survey Helping People Understand Soils • Definitions of the diagnostic horizons and required characteristics for mineral and organic soils are in Ch. 3 of KST • You need to be familiar with these for the soils in your area

25. Using the Keys Correctly Soil Survey Helping People Understand Soils • 2nd edition of ST has more in-depth discussions than KST on the diagnostic horizons and required characteristics • Realize that each new edition of KST updates and supersedes the older version of the text or keys in ST

26. Using the Keys Correctly Soil Survey Helping People Understand Soils With a key, you must start at the beginning and systematically work your way down comparing your soil to the criteria • Don’t make a habit of jumping into the middle

27. Using the Keys Correctly Soil Survey Helping People Understand Soils Chapter 17 (KST) has the information needed for family level differentiae • Separate sections for mineral and organic soils • 9 family classes, but there are different rules for when they are used • There are varying rules for identifying control sections • Each is arranged as a key

28. Using the Keys Correctly Soil Survey Helping People Understand Soils Appendix • Gives a brief description of the physical, chemical, and mineralogical laboratory determinations as used in ST • Remember: We use “operational definitions” • Full details are in the Lab Methods Manual Rounding • Pay attention to decimal points in criteria and use conventional rules for rounding

29. Summary Soil Survey Helping People Understand Soils • Soil taxonomy helps us organize our knowledge, communicate about soils, and transfer experience • Soil taxonomy adheres to 8 fundamental attributes • It is a 6-category hierarchical system with general concepts for each level • Definitions of criteria are operational

30. Summary Soil Survey Helping People Understand Soils • The 2nd edition of Soil Taxonomy (1999) has in-depth discussion of many aspects of the system not present in Keys to Soil Taxonomy but • Each new edition of the Keys to Soil Taxonomy updates and supersedes the older version of the text or keys in ST